1. Field of the Invention
The present invention relates to a conveyor apparatus which includes paired upstream belts and paired downstream belts and in which sheets held between the upstream belts are successively transferred to the downstream belts, whereby the sheets are conveyed while their conveyance speed is changed. In particular, the present invention relates to a conveyor apparatus of such a type suitable for conveyance of sheets folded into signatures by means of a folder added to a rotary press or the like.
2. Description of the Related Art
In general, rotary presses are equipped with folders for folding printed web. Some folders are equipped with a conveyor apparatus for reducing the conveyance speed of signatures before they enter a folding stage. FIG. 4 shows an example conveyer apparatus provided in such a folder (see, for example, Japanese Patent Publication (kokoku) No. H2-62456 and Japanese Patent Application Laid-Open (kokai) No. H11-60056).
In FIG. 4, reference numeral 11 denotes a transfer cylinder; 12 and 13 each denote a set of upstream-side upper rollers; 19 denotes a set of upstream-side upper belts; 21 to 25 each denote a set of upstream-side lower rollers; 29 denotes a set of upstream-side lower belts; 31 to 33 each denote a set of downstream-side upper rollers; 39 denotes a set of downstream-side upper belts; 41 to 44 each denote a set of downstream-side lower rollers; and 49 denotes a set of downstream-side lower belts.
The upstream-side upper rollers 12 (13) are rotatably provided on an unillustrated support shaft at predetermined axial intervals. The upstream-side upper belts 19 are wound around the transfer cylinder 11 and the upstream-side upper rollers 12 and 13 so as to connect them.
The upstream-side lower rollers 21 (22-25) are rotatably provided on an unillustrated support shaft at axial intervals identical to those of the upstream-side upper rollers 12 (13) such that the upstream-side lower rollers 21 (22-25) are located in the same vertical planes in which the upstream-side upper rollers 12 (13) are located, respectively. The upstream-side lower belts 29 are wound around the upstream-side lower rollers 21 to 25 so as to connect them, whereby the upstream-side lower belts 29 face the corresponding upstream-side upper belts 19 and can nip a signature in cooperation therewith.
The downstream-side upper rollers 31 (32, 33) are rotatably provided on an unillustrated support shaft such that the downstream-side upper rollers 31 (32, 33) and the upstream-side upper belts 19 are alternately located. The downstream-side upper rollers 31 are located on the upstream side of the upstream-side upper rollers 12 and 13. The downstream-side upper belts 39 are wound around the downstream-side upper rollers 31 to 33 and other, unillustrated downstream-side upper rollers so as to connect them, whereby upstream portions of the downstream-side upper belts 39 are located in the corresponding spaces between the upstream-side upper belts 19; i.e., these upstream portions overlap the upstream-side upper belts 19 in the horizontal direction.
The downstream-side lower rollers 41 (42-44) are rotatably provided on an unillustrated support shaft such that the downstream-side lower rollers 41 (42-44) are located in the same vertical planes in which the downstream-side upper rollers 31 (32, 33) are located, respectively. The downstream-side lower rollers 41 are rotatably supported on the same support shaft of the upstream-side lower rollers 23. The downstream-side lower belts 49 are wound around the downstream-side lower rollers 41 to 44 and other, unillustrated downstream-side lower rollers so as to connect them. Thus, upstream portions of the downstream-side lower belts 49 are located in the corresponding spaces between the upstream-side lower belts 29; i.e., these upstream portions overlap the upstream-side lower belts 29 in the horizontal direction. Further, the downstream-side lower belts 49 face the corresponding downstream-side upper belts 39 and can nip a signature in cooperation therewith.
Of the downstream-side upper rollers 31 to 33, the upper rollers 31, located furthest upstream, are positioned such that portions of the downstream-side upper belts 39 located furthest upstream are located above the upstream-side upper belts 19. Meanwhile, of the upstream-side upper rollers 12 and 13, the upstream-side upper rollers 12, located on the downstream side of the upstream-side upper rollers 13, are positioned such that portions of the upstream-side upper belts 19 located furthest downstream are located above the downstream-side upper belts 39.
In such a conveyor apparatus, the upstream-side upper belts 19 and the upstream-side lower belts 29 are caused to travel at a speed corresponding to the circumferential speed of the transfer cylinder 11, and the downstream-side upper belts 39 and the downstream-side lower belts 49 are caused to travel at a speed slower than the traveling speed of the upstream-side belts 19 and 29. When a signature is transferred from the transfer cylinder 11 to be fed between the upstream-side belts 19 and 29, the signature is held between and conveyed by the upstream-side belts 19 and 29. As a result, the downstream-side upper belts 39 gradually come into contact with the signature, and after the signature is transferred from the upstream-side lower belts 29 to the downstream-side lower belts 49, the upstream-side upper belts 19 gradually separate away from the signature. Thus, the signature is properly transferred, without generation of unintended positional shift in the conveyance direction, and fed between the downstream-side belts 39 and 49, which are slower than the circumferential speed of the transfer cylinder 11, whereby the signature is conveyed to a folding stage.
Incidentally, the thickness and length in a conveyance direction of signatures transferred from the transfer cylinder 11 may change depending on folding specifications such as double folding, triple folding, or quarto folding, the specifications of paper, and the like. Therefore, when the folding specifications or the paper specifications are changed, in some case, a shift in the conveyance direction is produced when a signature is transferred from the upstream-side belts 19 and 29 to the downstream-side belts 39 and 49.
Such a problem may occur not only in a conveyer apparatus which conveys sheets folded into signatures by means of a folder attached to a rotary press or the like, but also other conveyor apparatuses, each of which includes paired upstream belts and paired downstream belts and in which sheets held between the upstream belts are successively transferred to the downstream belts, whereby the sheets are conveyed while their conveyance speed is changed.